In the case where encrypted digital content is stored on various recording media and circulated, or is circulated via a network, the digital content is exposed to an attack of estimating a content key for decrypting the digital content. Therefore, a technique has been proposed where a part of the digital content is separated from a digital content body and distributed together with a license, to thereby protect the digital content.
However, in the conventional technique, because there is only one separation data separated from the digital content body, the proportion of a region which cannot be used in the digital content body has been small. Therefore, if a third person who has acquired the digital content body can estimate the content key of the digital content body, he/she may be able to use the digital content to some extent, even in a state where the separation data cannot be used.